Conventional folding knives ordinarily have a blade with a tang pivoted at one end to one of the ends of the knife housing that constitutes a handle. A friction type rib or spring keeps the blade in closed position. The blunt edge of the blade must be gripped and tugged to pull the blade from its closed or stored position. Some blades have an exposed groove along the blunt edge to receive an operator's fingernails as he tugs the blade open. Spring latching mechanisms or cams for temporarily locking the blade in open position are relatively weak such that minor forces or nudges override the latching mechanisms. This creates a dangerous condition in which the blade will collaspe upon the unwary operator's hand, cusing pain and injury.
There is one type of knife that has a positive lock of the blade in open position. This is done by means of a resilient rib on the back edge having a locking end engaging a notch in the end of the tang on the blade. The other end of the rib, or trigger, when depressed pivots and releases the locking end from the tang of the blade, freeing the blade to be moved to its closed position. The blade is frictionally retained in closed position and thus has the same problem in opening as the others. Such a knife cannot be disassembled or easily cleaned.